Isolated chimeric proteins of modified lumazine synthase

ABSTRACT

Isolated chimeric proteins including up to ten copies of peptides, polypeptides or protein domains inserted in the amino termini of the  Brucella  spp. Lumazine synthase enzyme. Isolated nucleotide sequences codifying the chimeric proteins. Vectors, plasmids and transformed cells used for expressing the proteins. Monoclonal and polyclonal antibodies induced by the chimeric proteins. Hybridomas producing the monoclonal antibodies. Vaccines and pharmaceutical compounds including the chimeric proteins, nucleotide sequences and antibodies. A method to induce an immune response in higher organisms including the administration of effective amounts of the vaccines and pharmaceutical compounds. Biosensors including the chimeric proteins. Protein conjugates formed by the chimeric proteins and a ligand bound by means of covalent and noncovalent bonds. Uses of the chimeric proteins, nucleotide sequences, vectors, plasmids, transformed cells, antibodies, hybridomas, conjugates, biosensors, vaccines and pharmaceutical compounds. The quaternary structure of the chimeric proteins.

This application claims priority from PCT Application No. PCT/US2005/019289, filed Jun. 3, 2005, and from Argentine Patent Application No. P 04 01 01923, filed Jun. 3, 2004, which applications are incorporated herein by reference.

TECHNICAL DESCRIPTION OF THE INVENTION

Isolated chimeric proteins including up to ten copies of peptides, polypeptides or protein domains inserted in the amino termini of the Brucella spp, lumazine synthase enzyme. Isolated nucleotides sequences codifying the chimeric proteins. Vectors, plasmids and transformed cells used for expressing the proteins. Monoclonal and polyclonal antibodies produced by such chimeric proteins. Hybridomas producing monoclonal antibodies. Vaccines and pharmaceutical compounds including the chimeric proteins, nucleotide sequences and antibodies. A method to induce an immune response in higher organisms including the administration of effective amounts of the vaccines and pharmaceutical compounds. Biosensors including the chimeric proteins. Protein conjugates formed by the chimeric proteins and a ligand bound by means of covalent and noncovalent bonds. Uses of the chimeric proteins, nucleotide sequences, vectors, plasmids, transformed cells, antibodies, hybridomas, conjugates, biosensors, vaccines and pharmaceutical compounds. The quaternary structure of the chimeric proteins.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to chimeric proteins formed by modified proteins derived from the lumazine synthase enzyme of Brucella spp., linked to peptides, polypeptides or proteins domains. The chimeric proteins are useful for inducing immune responses in higher animals and for other purposes. The present invention relates also to pharmaceutical compounds including antigens or antibodies, or segments of antigens or antibodies, bound to the modified proteins.

BACKGROUND OF THE INVENTION

The massive application of live-attenuated vaccines offer several economic and health inconveniences. When live vaccines are attenuated their immunogenic capability is often reduced. See Leclerc, et al., Immunol. Today, 19(7):300-302, (1998); Nieba, et al., Mod. Asp. Immunobiol., 1(2):36-39 (2000). Another inconvenience is the possibility that the attenuation be reverted and that the microorganism regain its disease inducing properties. See Redfield, N., N. Eng. J. Med., 316:673-678 (1998). Hence, during the past years, the trend has been to formulate acellular vaccines, based on individual compounds isolated from bacteria or virus. In general, these individual compounds, like proteins typical of a microorganism, have low immunogenicity. This limitation has been overcome by using adjuvant substances. However, there are proteins that even in the presence of adjuvant substances continue showing low immunogenicity. Several protein engineering strategies have been proposed to overcome these difficulties. See Leclerc, et al., Immunol. Today, 19(7):300-302 (1998).

Viral capsid proteins are able to form tridimensionally ordered particles, called “virus-like particles”. These particles have the same size and shape as whole viruses. However, they are empty inside and without genetic material rendering then incapable of producing infections. Their great size and order provide them with a marked immunogenicity. See Bachmann, et al., Science, 262:1448-1451 (1993). The recombinant vaccine against hepatitis B, widely accepted in the market, is based on this concept. The “virus-like particles” have been used as a vehicle for inserting peptides characteristic of certain pathogens with the aim of producing vaccines against such pathogenic microorganisms. See WO0032227 (Renner, et al.); WO0185208 (Bachmann, et al.). A favored strategy has been the insertion of multiple copies of a peptide in a very immunogenic vehicle, in order to provide a peptide with the adjuvant property of the carrier. However, this approach has encountered many difficulties: owing to the huge size of these particles, any insertion of a peptide in its compounding protein obstructs its proper folding and, in many cases, decreases its stability. Moreover, there are few sites able to accept peptide insertions without changing their general structure. See Nieba, et al. Mod. Asp. Immunobiol, 1(2):36-39 (2000).

Some bacterial proteins have been postulated as vehicles for developing chimeric vaccines. See Leclerc, et al., Immunol. Today, 19(7):300-302 (1998). The subunit B of the cholera toxin is a stable pentameric protein that has been used to obtain an immune response from the mucosa against inserted peptides. This strategy has been successful due to this toxin capacity to penetrate the gastric mucosa. See Arakawa, et al. Nature Biotech., 16:934-938 (1998). The dihydrolipoyl dehydrogenase enzyme of the Bacillus steearothermophilus has also been postulated as a proteic vehicle because it forms a complex and very stable polymeric structure. See Domingo, et al., J. Mol. Biol., 305:259-267 (2001); WO0142439 (Domingo, et al.).

The lumazine synthase enzyme catalyzes the penultimate step in the riboflavin biosynthetic route. See Goldbaum, et al., J. Med. Microbiol., 48:833-839 (1999). Its active site is located in the interphase among monomers, making this protein to have a very stable polymeric order. See Ritsert, et al. J. Mol. Biol., 253:151-167 (1995). These orders vary between proteins forming pentameric and icosahedric particles. See Braden, et al., J. Mol. Biol., 297:1031-1036 (2000). The icosahedric structure of the lumazine synthase of B. subtilis has been postulated as a vehicle for inserting peptides and developing vaccines. See WO0053229 (Bacher, et al.).

The lumazine synthase of Brucella spp. is a highly stable protein. It has been demonstrated that this 18-kDa protein is a useful marker for the serological diagnosis of human and animal brucellosis. See Goldbaum, et al., J. Clin. Microbiol., 30:604-607 (1992); Goldbaum, et al., J. Clin. Microbiol., 31:2141-2145 (1993); Baldi, et al., Clin. Diag. Lab. Immunol., 3 (4):472-476 (1996). According to immunochemical enzymatic function and tridimensional structure by X-ray crystallography analyses the original and modified protein shows the same when expressed recombinantly as the native protein. See Braden, et al. J. Mol. Biol., 297:1031-1036 (2000); Goldbaum, et al., J. Med. Microbiol., 48:833-839 (1999); Goldbaum, et al., J. Struct. Biol., 123:175-178 (1998). The structure shows that this 18-kDa protein behaves as a 180-kDa decamer in solution, becoming a new type of quaternary arrangement of the lumazine synthase. See Zylberman, et al., J. Biol. Chem., 279(9):8093-8101 (2004).

It has been postulated that the immunogenicity of the lumazine synthase of Brucella spp. derives mainly from its polymeric character. See Baldi, et al., Braz. J. Med. Biol. Res., 33:741-747 (2000). The structure also shows that the amino termini end of 10 aminoacids is involved neither in the general folding nor in the contacts among monomers. See Braden, et al. J. Mol. Biol., 297:1031-1036 (2000). The lumazine synthase of Brucella spp. is a powerful immunogen capable of producing a high humoral and cellular immune response in the murine model. This capability has been verified when the immunization is induced with the recombinant and modified protein and with a plasmid that codifies for the protein (gene therapy, DNA vaccination). See Velikovsky, et al., J. Immunol. Meth., 244(1-2):1-7 (2000). It is possible to modulate the response by changing the immunization route and the adjuvant used. See Velikovsky, et al., Infec. Immun., 70(5):2507-11 (2002). Particularly, it is possible to create a strong response of the T_(H)1 type, which would be the response with the highest protecting capacity in brucellosis. See Velikovsky, et al. Infec. Immun., 70(5):2507-11 (2002).

However, it is still a need in the art for new vehicles with smaller stable structures useful for displaying peptides, polypeptides and proteins, in general, and antigens or immune response-inducing agents, in particular. The development and use of the lumazine synthase decameric structure as a vector of this type have not been described in the art.

Deposit of Microorganisms

The pBLS-OMP31 plasmid was deposited on Apr. 1, 2004, under access number DSM 15546 in DSMZ—Deutsche Sammlung von Mikroorganismen und Zellkulturen, Mascheroder Weg 1B, D-38124 Braunschweig, Germany.

DIAGRAMS

FIG. 1 shows the nucleotide and amino acid sequence of the 5′ end of the gene of the cloned BLS gene in the expression vector pET11a (Novagen, USA) and the generated cassette (SEQ ID NOs: 24 and 25). The section in bold case shows the codifying region. The section in red case shows the mutated bases in the cassette. Section highlighted in yellow shows the new restriction sites.

FIG. 2 shows the oligonucleotides used to generate the BLS-OMP31 chimera (SEQ ID NO: 26). Their annealing produces the appearance of cohesive sites corresponding to the NsiI (5′ end) and AflII (3′ end) restriction enzymes, the sequence of 27 aminoacids inserted in the chimera (below, in bold case) being located among them (SEQ ID NO: 27). The theoretical molecular weight of the resulting protein monomer (19,977.5 Daltons) and the theoretical isoelectric point (pI=6.00) of the inserted peptide are also shown.

FIG. 3 shows: a) the pET11a plasmid scheme including the BLS-OMP31 chimera sequence, showing the restriction sites used when cloning, b) the complete nucleotide sequence of the pET11a plasmid including the BLS-OMP31 chimera and c) the open reading frame of the BLS-OMP31 chimera, and its amino acid sequence.

FIG. 4 describes the expression of BLS-OMP31 analyzed by SDS-PAGE in 17% acrylamide. MW. Molecular Weight Markers in KiloDaltons, 1: purified BLS, 2 and 3: aliquots of expression cultures of two BLS-OMP31 clones. The protein migrates like a 20-KDa monomer because the gel is denaturalizing.

FIG. 5 describes the expression of BLS-OMP31 analyzed by SDS-PAGE in 17% acrylamide. 1: culture without induction, 2: culture induced with 1 mM IPTG, 3: cytoplasmatic fraction, 4: fraction of inclusion bodies resuspended in 8M urea. The arrows show the bands corresponding to a BLS-OMP31. (LMWM=low molecular weight markers, weight indicated in kilodaltons).

FIG. 6 shows the chromatogram corresponding to the elution of the BLS-OMP31 in the Superdex 200 (Pharmacia, USA) column. The peaks were analyzed afterwards by gel and are numbered. See FIG. 7.

FIG. 7 shows the purification data of BLS-OMP31 analyzed by SDS-PAGE in 17% acrylamide. 1 and 2: peaks obtained by gradient of BLS-OPM31 elution of the Q-Sepharose (Pharmacia, USA) column. 4 and 5: the numbering of the peaks correlates to the peaks in FIG. 6. (LMWM=low molecular weight markers, weight indicated in kilodaltons).

FIG. 8 shows the circular dichroism spectra of BLS and the BLS-OMP31 chimera. The molar elipticity of a 1.0-μM solution of protein between 190 and 260 nm was monitored in a spectropolarimeter (Jasco, UK).

FIG. 9 describes a comparative analysis of the stability of the BLS-OMP31 chimera in relation to the native protein. The curves show the sensitivity to unfolding in the presence of growing concentrations of the denaturalizing guanidine hydrochloride chemical agent, evaluated by the elipticity developed by the protein in a spectropolarimeter at 222 nm.

FIG. 10 shows the antigenicity of BLS-OMP32 by ELISA. 1 ug, 0.25 ug, 0.1 ug and 20 ng of BLS-OMP31 and BLS were used as antigens. Anti-BLS Mab (1/1000) and Anti-OMP31 Mab (1/1000) were used as antibodies.

FIG. 11 shows the immunogenicity of BLS-OMP31 analyzed by ELISA. The reactivity of 1/100 dilutions of sera from mice immunized with BLS-OMP31 with adjuvant (“AF”) or without adjuvant (“PBS”) against OMP31 are shown. Sera of each group were ordered per decreasing reactivity. The reactivity of a pre-immune serum (negative control) is illustrated by a dot line. A mouse from the AF group died before the extraction.

FIG. 12 shows the titration results of an ELISA test of sera from anti BLS-OMP31 rabbit. The reactivity of the three sera against OMP31 was assayed. A 1/100 dilution of a serum of anti BLS-WT rabbit was used as a negative serum. The reactivity of this serum is illustrated by a dot line.

FIG. 13 describes the reactivity of an anti BLS-OMP31 rabbit serum (4° dose) against smooth or rough B. melitensis H38 whole bacteria. The reactivity corresponding to a rabbit anti native BLS serum, tittered simultaneously against both antigens, was substracted from the values shown. The errors correspond to the sum of mean standard errors.

FIG. 14 shows the kinetics of total anti-OMP31 IgG antibodies in mice batches BALB/c (8 per group) immunized in 4 occasions by intramuscular and intradermal route with 100 μg of pCI-BLS-OMP31. Antibodies levels were analyzed by ELISA every 15 days. The values represent the mean value of the 8 animals ±S.D. The arrows show the time of the immunization. Sera of pCI mice (control) showed n DO values similar to or lower than the “cut-off” criteria.

FIG. 15 describes: a) the oligonucleotide sequence used to obtain the BLS-KETc1 chimera (SEQ ID NO: 28), b) the complete nucleotide sequences of the pET11a plasmid including the BLS-KETc1 chimera and c) the open reading frame of the BLS-KETc1 chimera and its amino acid sequence.

FIG. 16 shows the general strategic scheme to produce mixed chimeras.

FIG. 17 shows the purification results and analysis of mixed chimeras created between the BLS-OMP31 and BLS-KETc1 chimeras. A: analysis by anionic interchange chromatography in MonoQ column of BLS-OMP31 (peak 3) and BLS-KETc1 (peak 1) refolded chimeras and the stoichiometric mixture of both (peak 2), B1: analysis through SDS-PAGE of peaks 1, 2 and 3 obtained in the anionic interchange chromatography, B2: Analysis through native PAGE of pure BLS-OMP31 and BLS-KETc1 chimeras and of peak 2 corresponding to the mixed chimeras.

FIG. 18 shows the immunogenicity of the BLS-OMP31-KETc1 mixed chimera analyzed by ELISA. Reactivity of 1/100 dilutions of sera from mice immunized with BLS-OMP31-KETc1 (empty bars) against BLS and against OMP31 and KETc1 synthetic peptides. The reactivity of a pre-immune serum (negative control) against the same antigens is indicated in gray bars.

FIG. 19 shows the in vitro proliferation of splenocytes induced by the immunization with BLS-KETc1. It indicates the average plus 1 standard deviation of the titrated (in cpm) timidine incorporation after the in vitro stimulations of splenocytes from mice previously immunized with KETc1 peptide or BLS-KETc1 emulsified in saponin. *Significant increase in cpm in respect of splenocytes incubated with a culture medium (P<0.05).

FIG. 20A and FIG. 20B describe the nucleotide and aminoacid sequence of the BLS-RBD3 chimera. The codifying sequence of domain RBD3 of the murine protein Staufen-1 is shown in red case. The codifying sequence of the truncated BLS in the first 8 residues of its amino termini is shown in black case.

FIG. 21 shows the structure of the BLS-RBD3 chimera (panel A: side view, panel B: upper view). The structure was designed with the MacroModel program merging the C-terminal end with the theoretical structure of the domain RBD3 of the murine protein Staufen-1 (shown in a blue range of colors) with the N-terminal end of the BLS crystallographic structure (Protein DataBank file pdb: 1DIO) (shown in a red range of colors). The theoretical structure of domain RBD3 of the murine protein Staufen-1 was built by means of homology modeling with the structure of the domain RBD3 of the protein Staufen of Drosophila melaganoster (pdb: 1EKZ). The figure was built with the CHIMERA program.

FIG. 22 shows: A: the separation of the BLS-RBD3 chimera by SDS-PAGE in a 15% polyacrilamid gel (P/V), various molecular weight markers were run in the right pathway. B: the circular dichroism spectrum in the UV far from the BLS-RBD3 chimera. The figure comparatively shows the chimera spectrum measured experimentally (in a continuous line) and its theoretical spectrum (in a dot line), calculated from the combination of the spectra corresponding to BLS protein and RBD3 domain of the murine protein Staufen-1 in isolation. The measurement was performed in a 50 mM Tris/HCl, 1.2 M NaCl, pH 8 buffer, at 4° C. C: the assessment of molecular weight of the BLS-RBD3 chimera by using a light scattering detector connected in series to the outlet of a molecular filtering column and an refraction index (RI) detector. BLS-RBD3 was run in a Superdex-200 column and eluted with a 50 mM Tris/HCl, 3 M urea, 1 M NaCl, pH 8 buffer, at a flow of 0.5 ml/min. The elution was monitored by measuring its light scattering signal at 90 degrees and light refraction (LR). The sample molecular weight was calculated by comparing the relationship of its light scattering and refraction signals with those of a bovine seroalbumin sample used as a reference pattern (BSA molecular weight: 66.5 kDa).

FIG. 23 shows the optical density obtained at 492 nm of the 1/100 dilution of sera analyzed for each mice of each investigational group. The result at 30-day interval after the second immunization is shown as a representative example. The horizontal line represents the mean value of each group.

FIG. 24 shows the results of an anti-OMP31 Mab ELISA test.

FIG. 25 shows the detection of anti-OMP31, AcMo37F7 monoclonal antibody, using a biosensor formed by derivatization with the BLS-OMP31 chimeric protein.

FIG. 26 shows the expression of costimulating molecules in dendritic cells stimulated with BLS. Dendritic cells, derived from the bone marrow, were incubated during 18 hs with BSL (BLS 10 μM) or with medium only (control). The expression of CD40 in CD11c⁺ cells (A) and of I-A^(d) in CD11c⁺ (B) is shown. The isotype controls are shown to the left of each graph.

FIG. 27 shows the strategy followed to form molecular assemblies with complementary heterodimeric peptides incorporated into the modified BLS protein and a theoretical X antigen target. See Braden, et al., supra. A Swisspdbviewer modeling software was used.

FIG. 28A and FIG. 28B show the nucleotide sequence of the BLS-RR₁₂EE₃₄₅L insert gene cloned in the expression vector pET11a (Novagen, USA) (SEQ ID NO: 31). The section in red case shows the codifying region of the BLS-RR₁₂EE₃₄₅L insert peptide. The section in black case shows the codifying region for the modified BLS protein.

FIG. 29 describes the nucleotide and amino acid sequences of the BLS-RR₁₂EE₃₄₅L fusion protein (SEQ ID NOs: 19 and 8, respectively). The section in red case shows the codifying region of the RR₁₂EE₃₄₅L peptide. The section in black case shows the codifying region for the modified BLS protein. The section in green case shows the position of K₄₉ residue substituted with serine.

FIG. 30 shows the separation of the BLS-RR₁₂EE₃₄₅L fusion protein by SDS-PAGE in a 17% polyacrylamide gel. 1: molecular weight markers, 2: irrelevant sample, 3: fusion protein BLS-RR₁₂EE₃₄₅L.

FIG. 31 shows the assessment of molecular weight of the BLS-RR₁₂EE₃₄₅L chimera by using a light scattering detector serially connected to the outlet of a molecular filtering column and a refraction index (RI) detector. BLS-RR₁₂EE₃₄₅L was run in a Superdex-200 column and eluted with a 50 mM Tris/HCl, 3 M urea, 0.1 M NaCl, pH 8 buffer, at a flow of 0.5 ml/min. The elution was monitored by measuring its light scattering signal at 90 degrees and light refraction (LR). The sample molecular weight was calculated by comparing the relationship of its light scattering and refraction signals with those of a bovine seroalbumin sample used as a reference pattern (BSA molecular weight: 66.5 kDa).

FIG. 32 shows the nucleotide sequence of the peptide EE₁₂RR₃₄₅L insert gene cloned in the expression vector pGEX-4T1 (Novagen, USA) (SEQ ID NO: 32). The sequence is inserted between the BamH1 y EcoR1 restriction sites of the vector. The section in black case shows the codifying region for GST protein. The section in red case shows the codifying region for the peptide EE₁₂RR₃₄₅L.

FIG. 33 shows the nucleotide sequence of the peptide GST-EE₁₂RR₃₄₅L insert gene cloned in the expression vector pGEX-4T1 (Novagen, USA) and the corresponding amino acid sequence (SEQ ID NOs: 33 and 34, respectively).

FIG. 34 shows the molecular assembly between fusion protein BLS-RR₁₂EE₃₄₅L and peptide EE₁₂RR₃₄₅L.

FIG. 35 shows 10 EE₁₂RR₃₄₅L peptides coupled to the BLS-RR₁₂EE₃₄₅L decamer.

DESCRIPTION OF THE INVENTION

The present invention describes chimeric proteins useful, in general, for displaying peptides, polypeptides and proteins. The peptides, polypeptides and proteins shown herein may induce an immune response or be suitable for other useful purposes.

The present invention also describes pharmaceutical compounds and vaccines of high immunogenic value and efficacy. These compounds and vaccines include chimeric proteins generated by using the lumazine synthase enzyme of Brucella spp. (BLS) as an immunogenic vehicle.

The chimeric proteins described in this application can display peptides, polypeptides, proteins or molecules of other distinctive pathogens and non-pathogens types.

More specifically, the chimeric proteins described in this application can be useful for the treatment and prevention of human diseases. These entities can be used for the inoculation of antigens, toxins and protein domains with low or without immunogenic activity. Examples of these indications would be vaccination against common measles, German measles (rubella), hepatitis, tetanus, pertussis, poliomyelitis, diphtheria, mumps, meningitis and rabies, in infants. Other examples of these indications are the vaccination against hepatitis A, B and C, influenza, encephalitis, rabies, typhoid fever, yellow fever, herpes simplex, varicella zoster, dengue, human papillomavirus, cholera, malaria, tuberculosis and mumps in adults. Other examples of these indications are vaccines useful to counteract bioterrorism, for the following pathogens: Botulinum toxin, Bacillus anthracis, Clostridium perfringens, Bacillus subtilus, Bacillus thuringiensis, hemorrhagic conjunctivitis virus (Enterovirus 70) and rotavirus.

These entities can also be used for the treatment of chronic conditions, such as Alzheimer's disease, Parkinson's disease and rheumatoid arthritis or other conditions, such as allergies and tumors. An example of the latter could consist of a chimeric protein simultaneously including antibodies or fragment of antibodies against tumoral markers or radioactive elements for radiotherapy. The chimeric proteins developed according to the present invention, and the antibodies derived from them, could also be used for the diagnosis of fertility and pregnancy, or of diseases such as colon, lung, breast and prostate cancer. These entities could also be used to monitor and control drug abuse or the progress for therapeutic treatments.

The chimeric proteins described in the present invention also have multiple uses for the breeding domestic animals, farm animals and fish. These entities may be used to prepare vaccines against Brucella spp., a bacterial agent that causes many problems in cattle, or against Piscirickettsia salmonis, which mainly affects the commercial breeding of salmon. Moreover, these entities can be useful to administer antibacterial agents, such as penicillin, amoxicillin or other penicillin subproducts, alone or in combination with specific antibodies to domesticated animals, like cats and dogs, or farming animals, like cattle.

Other possible uses of the chimeric proteins described in this application are the preparation of vaccines against Mycoplasma hyopneumoniae, a pneumonic agent that produces great losses in pigs, and administration of parasiticides, like albendazole, fenbendazole and ivermectin against Ostertagia ostertagi, to calves and cattle in general. It would also be possible to use these new entities to administer parasiticides, like abamectine and praziquantel, to horses and to vaccination with epitopes of antigens or viral protein domains, like poultry influenza, to birds. In all cases, the chimeric protein can simultaneously contain the parasiticide agent and the specific antibodies against the involved parasite. An additional therapeutical use of the new entities would be the administration of antiinflammatory agents, like carprofen to domesticated animals, like dogs and cats.

The chimeric proteins according to the present invention could also have different indications for the control of pathogens. These entities could be used to modify the expression of certain hormones to accelerate the growth rate and increase the production of milk, in farming animals or make their meat leaner. An example of these non-conventional indications would be the use of these entities for immunocastration of farming animals, like pigs.

The chimeric proteins described in this application can also be used for the large-scale production of vaccines and antibodies in molecular farming. Under this approach, the vaccine or antibody will be expressed firstly in a suitable plant. The vaccine or antibody will then be extracted and purified to prepare a pharmaceutical formulation. Another possibility would be to feed animals with plants so transformed with the entities described herein to immunize via their food intake (edible vaccines).

A particular advantage of the present invention is that the vehicles described herein are able to carry peptides larger than other vehicles known in the art, such as the “virus like particles”. This advantage is due to their small size and higher stability. This antigenic display system of the vehicles described herein has the additional advantage of displaying peptides, polypeptides and proteins inserted repeatedly and ordered spatially, increasing their stability and half-life. The carrier protein (BLS) also has a considerable adjuvant effect on peptides, polypeptides and proteins inserted thus enhancing the immune response effectiveness.

Another advantage of the present invention is that the carrier protein BLS induces an immune response by itself without the presence of additional adjuvants. This characteristic facilitates the administration of vaccines prepared according to the present invention by various routes of administration (e.g., intravenous, nasal, oral, needle-free) with or without adjuvants.

The pharmaceutical compounds and vaccines described in this application are characterized by their high stability at room temperature. This characteristic would likely preserve the compound or vaccine without keeping a strict cold chain of storage.

The creation of mixed chimeras with multiple peptides inserted in the different ends of the carrier protein BLS is also useful to design multivalent vaccines or vaccines aimed at different routes of immune response. The prevailing opinion in the art at present is that a vaccine should not contain more than 10 immune response-inducing agents. It is also the prevailing opinion in the art that the vaccine should contain 5 or less inducing agents to achieve optimal results.

The chimeric proteins described in this application are useful for the production of antibodies. These antibodies and their associated entities could be used in diagnosis. It is also possible to develop kits for the diagnosis of diseases using the above-mentioned antibodies and associated entities.

Several of these entities developed according to the present invention could be also used to display peptides and build protein libraries and their associated applications (e.g., combinational biology applied to the identification of molecules for the development of drugs or the identification of polypeptide sequences binding preferably inorganic compounds, for nanobiological applications). Some of these new entities could also be used for the production and assembly of nanotechnologic devices or for the conduction of nanotechnologic processes.

The chimeric proteins according to the present invention could be used in the construction and development of biosensors applied to the analytical detection of several substances and molecules (e.g., detection of contaminants or toxins in water, soil or air, detection of residues of drugs, herbicides and pesticides in food).

Another advantage of the entities described in this present application is its easy and low-cost production. The chimeric proteins described in this application are obtained in high amounts from a model of transformed strains from E. coli, a microorganism of well-known management and culture. The proteins of interest obtained according to this method are easily purified from the culture medium.

In a version of this present invention, the isolated chimeric proteins claimed herein are formed by a peptide, polypeptide or protein linked to a protein mutated from the lumazine synthase of Brucella spp. whose codifying nucleotide sequence has been modified in its first 8 residues as its N-termini to allow its cleavage by restriction enzymes that do not cleave naturally the codifying nucleotide sequence of the native lumazine synthase protein of Brucella spp. Preferably, the codifying nucleotide sequence of the mutated lumazine synthase of Brucella spp. protein has been modified for the first 8 residues at its N-termini in order to allow its cleavage with the Nsi I and Afl II restriction enzymes. More preferably the mutated lumazine synthase proteins used according to the present invention have the amino acid sequences SEQ ID NO:1, SEQ ID NO:2, SEQ ID NO:3, SEQ ID NO:4, SEQ ID NO:5, SEQ ID NO:6, SEQ ID NO:7. The linked peptide, polypeptide or protein can be homologous or heterologous. In a version of the present invention, the peptide linked to the mutated protein is a heterodimerization domain. Preferably, this heterodimerization domain is a “leucine zipper” domain. The chimeric proteins thus obtained include, but are not limited to, the amino acid sequence SEQ ID NO:8 and are used preferably for the coupling of protein domains, complete proteins or other non-protein entities. In another version of this invention, the combinations of isolated chimeric proteins described in this present application are also claimed. The uses of these isolated chimeric proteins and of their combinations are also claimed.

In another embodiment of the present invention, the isolated codifying nucleotide sequences for the chimeric proteins described in this application are claimed. These sequences can be of RNA, genomic DNA or copy DNA. In another embodiment of the present invention, the codifying sequence for the linked peptide, polypeptide or protein is located in the 5′ region of the codifying nucleotide sequence for the mutated lumazine synthase protein of Brucella spp. In another embodiment of the present invention, the codifying sequence for the linked peptide, polypeptide or protein is operatively linked to the 5′ region of the codifying nucleotide sequence for the mutated lumazine synthase protein of Brucella spp. Preferably the following DNA sequences utilized are: SEQ ID NO:12, SEQ ID NO:13, SEQ ID NO:14, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:17, SEQ ID NO:18 and SEQ ID NO:19. Specific instances of the mutated protein sequences used in the present invention include, but are not limited to, the framework nucleotide sequences: a) BLS-OMP31b) BLS-KETc1 and c) BLS-RBD3, used in Examples 1, 5 and 8, respectively. In another embodiment of this invention, the combinations of isolated nucleotide sequences described in this present application are claimed. The uses of these isolated nucleotide sequences and their combinations are also claimed.

In another embodiment of the present invention, the combinations of isolated chimeric proteins and the isolated nucleotide sequences described in the present invention are claimed.

In another embodiment of the present invention, the vectors including the codifying sequences for the chimeric proteins described herein are claimed. These vectors can be bacterial, viral or other origin, and are able to express, or facilitate the expression of the chimeric proteins described in the present application. Specific instances of these vectors are pBLS-OMP31, pBLS-KETc1 and pBLS-RBD3 plasmids, used in Examples 1, 5 and 8, respectively. Preferably, the pBLS-OMP31, DSM 15546 plasmid is used as a vector and as a precursor for the generation of plasmids expressing the chimeric proteins described in the present application. The uses of these vectors are also claimed.

In another embodiment of the present invention, the cells or microorganisms transformed with the vectors described in this application are claimed. These microorganisms could be of prokaryote, eukaryote or other origin. Specific instances of the cells that can be transformed with the vectors described in the present invention include, but are not limited to, insect cells, bacteria, such as Escherichia coli, and mammal cells, such as CHO, COS, BHK, Namalwa and HeLa. More preferably, competent strains of Escherichia coli are used for such transformations. The uses of these cells are also claimed.

In a version of present invention, the isolated chimeric proteins described herein are able to induce an immune response in a eukaryote organism. These chimeric proteins can induce cellular or humoral responses in the treated organism. In these cases, the response could be against the same antigen, toxin, protein domain or inducing agent or against different antigens, toxins, protein domains or inducing agents. The antigens, toxins, protein domains or agents used according to the present invention could be of bacterial, parasitic, viral or other origin, and be able to induce an immune response. Specific instances of these inducing agents include, but are not limited to the: a) the 27 amino acid sequence of the OMP31 protein of Brucella mellitus, b) the 14 amino acid sequence of the KETc1 protein of Tenia solium and c) the 75 amino acid sequence of the RBD3 domain of murine protein Staufen, used in Examples 1, 5 and 8, respectively. In general, the treated eukaryote organisms are birds, fish or mammals. Preferably, these organisms are from a murine, rabbit or human origin. More preferably, the organism is of human origin. The uses of these chimeric proteins able to induce an immune response are also claimed.

In a version of present invention, the codifying nucleotide sequences for the isolated chimeric proteins described herein are able to induce an immune response in an eukaryote organism. These nucleotide sequences can induce cellular or humoral responses in the treated organism. In these cases, the response can be against the same antigen, toxin, protein domain or inducing agent or against different antigens, toxins, protein domains or inducing agents. The antigens, toxins, protein domains or inducing gents used according to the present invention can be of bacterial, parasitic, viral or other origin, and are able to induce an immune response. Specific instances of these inducing agents include, but are not limited to, the codifying nucleotide sequences for: a) the 27 amino acids of the OMP31 protein of Brucella melitensis, b) the 14 amino acids of the KETc1 protein of Tenia solium and c) the 75 amino acids of the RBD3 domain of murine protein Staufen, used in Examples 1, 5 and 8, respectively. In general, the treated eukaryotic organisms are birds, fish or mammals. Preferably, these organisms are from a murine, rabbit or human origin. More preferably, the organism is of human origin. The uses of these nucleotide sequences able to induce an immune response are also claimed.

In a version of the present invention, pharmaceutical compound or vaccines including the following are claimed: 1) at least one type of the chimeric proteins described in this application, 2) at least one type of the codifying nucleotide sequences for the chimeric proteins described in this application or 3) a combination of 1 and 2).

The pharmaceutical formulations or vaccines claimed for in the present application can be in a liquid state or in any other pharmaceutical form known in the art, such as injectable emulsions. The pharmaceutical compounds or vaccines described in the present invention can also be in tablets, liquid solutions, suspensions or elixirs for oral administration or in sterile liquids such as solutions or suspensions. Preferably an inert medium is used, such as saline media, phosphate-saline buffers and any other medium where the chimeric proteins, nucleotide sequences or segments thereof have a proper solubility.

The active agents of the pharmaceutical compounds or vaccines claimed in this invention are present in effective physiological doses. These active agents can be administered alone or in combination with acceptable pharmaceutical excipients, such as adjuvants, in order to increase the production of antibodies.

The pharmaceutical compounds or vaccines according to the present invention include, but are not limited to, several oily formulations such the Freund adjuvant, tyrosin stearate, MDP dipeptide, saponin, aluminum hydroxide (alum), lymph cytokines, the native protein of the lumazine synthase of Brucella spp. and proteins mutated from the lumazine synthase of Brucella spp. described herein. See U.S. Pat. No. 4,258,029 (Moloney, et al.); U.S. Pat. No. 5,057,540 (Kensil, et al.). Preferably tyrosin stearate, aluminum hydroxide, the native protein of the lumazine synthase of Brucella spp. and the mutated proteins described herein are used in the case of human beings. The Freund adjuvant, though powerful, is not used usually in human beings. The pharmaceutical compound or vaccine can also be administered using slow releasing mechanisms, such as liposomes. See U.S. Pat. No. 4,235,877 (Fullerton, W.). The preparation of vaccines and pharmaceutical compounds for their use in higher organisms is known in the art. See Remington, et al., Pharmaceutical Sciences, Mack Publishing Co., Easton, Pa., 1980; Voller, et al., Eds., New Trends and Developments in Vaccines, University Park Press, Baltimore, Md., 1978.

In a version of the present invention, a method to induce an immune response in a eukaryotic organism is claimed. The method encompasses the administration to such organism of an effective amount of a pharmaceutical compound or vaccines including: 1) at least one type of the chimeric proteins described in this application, 2) at least one type of the codifying nucleotide sequences for the chimeric proteins described in this application or 3) a combination of 1 and 2). In a version of this invention, a humoral response is induced. In another embodiment of this invention, a cellular response is induced. In another embodiment of this invention, humoral or cellular responses are induced simultaneously or sequentially. In these cases, responses can be against the same antigen, toxin, protein domain or inducing agent or against different antigens, toxins, protein domains or inducing agents. The antigens, toxins, protein domains or agents used according to the present invention can be of bacterial, parasitic, viral or other origin, and are able to induce an immune response. Specific instances of these inducing agents include, but are not limited to, the nucleotide sequences codifying for or to the amino acid sequences of: a) the 27 amino acids of the OMP31 protein of Brucella melitensis, b) the 14 amino acids of the KETc1 protein of Tenia solium and c) the 75 amino acids of the RBD3 domain of murine Staufen protein, used in Examples 1, 5 and 8, respectively. Examples of organisms that may be treated with the vaccines and pharmaceutical compounds described in this application are birds, fish or mammals. Preferably, these organisms are from a murine, rabbit or human origin. More preferably, the organism is of human origin. The vaccines or pharmaceutical compounds described in the present invention can be administered in one or several doses. Preferably, the administration is performed in only one dose. The administration can also be performed by subcutaneous, intravenous, intramuscular, oral, nasal or needle-free route. Preferably, it is performed by subcutaneous or intramuscular route.

In another embodiment of the present invention, the monoclonal and polyclonal antibodies produced in response to the immunization with chimeric proteins and the nucleotide sequences described herein are claimed. The hybridomas developed for expressing and producing the antibodies described in this application are also claimed. The uses of these antibodies for their preventive, therapeutic, diagnostic and other purposes are claimed. The pharmaceutical compounds including the antibodies described herein and their uses are also claimed.

In another embodiment of the present invention, the protein conjugates formed between the chimeric proteins described herein and one ligand are claimed. In a version of this invention, the link between the chimeric protein and the ligand is covalent. In these cases, the link is preferably peptidic. In another embodiment of this invention, the link between the chimeric protein and the ligand is non-covalent. The uses of these protein conjugates are also claimed.

In another embodiment of the present invention, the typical quaternary structure of the chimeric proteins described herein is claimed.

As used herein, “active agent” is defined as: 1) genomic DNA, copy DNA, messenger RNA or segments thereof, codifying for the chimeric proteins, or fragments thereof, described in the present application and 2) the chimeric proteins, or segments thereof described in the present application, 3) the combinations of 1) and 2) or 4) the protein conjugates formed between the chimeric proteins described herein or segments thereof and other entities.

As used herein, the term “effective amount” is defined as a quantity sufficient to produce one or more of the following results: 1) induction of a proper immune response, whether humoral or cellular, including the production of antibodies against the inducing agent; 2) inhibition of the growth, development, size and motility of the cell or microorganism associated with the inducing agent. When the inducing agent is a tumor, the “effective amount” will be the quantity sufficient to reduce the size, to prevent growth, to inhibit the metastasis or tumor growth, or to relieve the discomfort caused by such tumor or to prolong the life of an individual suffering from such tumor.

As used herein, the term “mammal” is defined as a hot-blooded vertebrate animal whose descendants are fed with milk secreted by its mammal glands. The term “mammal” includes, but it is not limited to, rats, mice, rabbits, dogs, cats, goats, cows, sheep, pigs, primates and human beings.

As used herein, the term “pharmaceutical compound or vaccine” is defined as a diluent, adjuvant or excipient with which the active agent is administered jointly. It includes each and every solvent, dispersion media, aqueous and gaseous solutions, coatings, antibacterial and antifungal agents, isotonic agents, retardants or catalysts of absorption or similar substances. The use of such media and agents in the administration of active pharmaceutical substances is known in the art. The use of such conventional media with the active agent is indicated unless the active agent is rendered ineffective by the media. Supplementary active principles can also be incorporated into the active agents described in the present invention. The term “pharmaceutical compounds or vaccines” include, but are not limited to, inert solvents or excipients, sterile aqueous solutions and several non-toxic organic solvents. The “pharmaceutical compounds or vaccines” should neither react with nor otherwise reduce the efficacy or stability of the active agent. The acceptable pharmaceutical vehicles include, but are not limited to, water, ethanol, polyethileneglycol, mineral oil, petrolatum, propyleneglycol, lanolin and similar agents. The “pharmaceutical compounds or vaccines” for injectable use include sterile aqueous solutions (when soluble in water) or sterile dispersions and powders for preparing sterile injectable dispersions or solutions. In every case, the formulation should be sterile and preferably fluid in order to enable its dispensing through a syringe. It should also be stable under manufacturing and storing conditions and should be protected from the contaminating effect of microorganisms such as bacteria, virus and fungi.

As used herein, the term “preventive use” is defined the capacity to induce and generate an immune response against one or more antigens, toxins, protein domains or other inducing agents, or segments thereof.

As used herein, the term “sequential administration” means that: 1) the same active agent is administered in more than one occasion at consecutive periods of time or 2) two or more active agents are administered alternatively in more than one occasion at consecutive periods of time. When the administration is “sequential”, the time difference between the administrations of active agents may be minutes, hours, days, weeks or months depending on whether the use is preventive or therapeutical and on the nature of the treated organism.

As used herein, the term “single or simultaneous administration” means that one or more active agents are administered in the same occasion at once.

As used herein, the term “therapeutic use” is defined to refer to every process, therapy or similar action, in which a higher organism, including a human being, is subject to medical care with the aim of improving such organism condition or resistance to diseases, whether directly or indirectly.

EXAMPLE 1 BLS-OMP31 Chimeric Gene Construction

This example describes the strategy used to insert the sequence corresponding to the 48 to 74 amino acids of the polypeptidic sequence of the OMP31 protein of Brucella melitensis into the 10 amino termini of the decamer forming the lumazine synthase of Brucella spp.

1. Mutation and Cloning

The pBLS-OMP31 plasmid, SEQ ID NO:23, was constructed through the following protocol:

-   -   a) To clone the codifying gene for the lumazine synthase of         Brucella spp. (BLS), the BLS sequence was obtained by PCR         amplification with specific primers from the genomic DNA of B.         abortus and cloned in the pET11a vector (Novagen, USA). The         pET11-BLS plasmid containing the open reading frame of the         lumazine synthase of Brucella spp. was digested further with the         Bam HI and XbaI restriction enzymes. The insert obtained was         subcloned in the pALter-Ex1 vector (Promega, USA).     -   b) A directed mutagenesis was performed over the sequence         codifying for the open reading frame of the lumazine synthase of         Brucella spp. (BLS). This sequence was cloned in the pALter-Ex1         vector (Promega, USA) using the ALTERED sitesII kit (Promega,         USA). In order to develop the cassette, two new restriction         sites were inserted in the 5′ region of the BLS gene: an Nsi         site in the first two codons of the 5′ end, and one AFL II site         in the two codons comprising the 8 and 9 residues of the native         amino acids sequence of BLS. It was taken into consideration         that these restriction sites do not occur in the native BLS gene         or in the pET11a vector. See FIG. 1.     -   c) The mutation was checked afterwards by sequencing. The         cassette including the mutated BLS sequence (SEQ ID NO:12), was         subcloned in the pET11a vector (Novagen, USA), to obtain the         plasmid called hereinafter pBSLm.     -   d) To insert the sequence corresponding to the OMP31 plasmid,         two oligonucleotides were designed so that they form a         double-stranded DNA and include the codifying sequence for the         48-74 aminoacids of the OMP31 protein of Brucella melitensis         protected by the cohesive ends typical of the Nsi I and Afl II         restriction enzymes when annealing. FIG. 2 shows the         oligonucleotides designed for constructing the pBLS-OMP31 and         the synthetic insert formed by these.     -   e) The pBLSm plasmid was digested with the Nsi I and Afl II         restriction enzymes. The codifying sequence corresponding to the         first 8 residues of the BLS was removed. The original BLS         sequence was changed for the nucleotide sequence of the inserted         OMP31 peptide in this case.     -   f) The synthetic insert of step d) above was linked to the open         pBLSm cassette obtained in step e) by incubating overnight with         DNA T4 ligase enzyme at 16° C. The insertion was confirmed by         sequencing. Thus, a gene with the SEQ ID NO:20 sequence was         obtained. The sequencing analysis showed that the first 8         aminoacids of the lumazine synthase of the Brucella spp. were         replaced by the 27 aminoacids from the 48-74 sequence of the         OMP31 protein of Brucella melitensis. This open reading frame         was called BLS-OMP31 chimera, of SEQ ID NO:20. Its corresponding         plasmid was called pBLS-OMP31, of SEQ ID NO:23. See FIGS. 3 b         and c.

This experiment was repeated using the DNA sequences of the mutated BLS SEQ ID NO:13, SEQ ID NO:14, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:17 and SEQ ID NO:18. Similar results were obtained.

2. Transformation

A competent strain of E. coli BL21 (DE3) bacteria was transformed by thermal shock with the pBLS-OMP31 plasmid obtained according to the protocol above. Afterwards, bacteria were cultured in agar plates including LB-agar/ampicilin to choose those transformed with the plasmid. 2 ml of a LB/ampicilin medium was inoculated to a colony extracted from agar plates for small-scale expression tests. The colony was shaked and incubated at 37° C. The saturated culture was induced with 2 μl of 1M.IPTG. Three hours later, 100 μl of culture was removed, centrifuged The resulting pellet was resuspended in 25 μl of sample buffer 1× for its analysis by SDS-PAGE 17%. See FIG. 4.

3. Expression and Purification of the BLS-OMP31 Chimeric Protein

A 5-ml preculture of the transformed strains was cultured to saturation according to the step above, with 500 ml of LB/ampicilin. The culture was incubated and shaked at 37° C. It was induced with 0.5 ml of IPTG (1M) to reach an optical density of 0.6-0.8 at 600 nm. The culture was removed three hours later and was centrifuged at 4000 g for 20 min. The pellet was suspended in 15 ml of suspension solution (50 mM Tris, 5 mM, EDTA, 1% Triton X-100, pH 8.0).

The suspension was sonicated at 1 minute intervals every minute for 5 minutes and was centrifuged at 20,000 g for 30 minutes. The pellet was resuspended in 15 ml of suspension solution without Triton X-100 and the sonicate process was repeated. The procedure was repeated for a third time. The chimera expressed in the cytoplasm was contained in three sonicate supernatants, while inclusions bodies were contained in the pellet. See FIG. 5.

The inclusion bodies were resuspended in PBS buffer with 8 M urea and were left overnight at room temperature. The resuspension was dialyzed against PBS for two days with a buffer change. The sample was centrifuged and the supernatant was dialyzed against buffer A (50 mM Tris/HCl, pH 8.5). The first purification step was performed by anionic interchange chromatography in a MonoQ or a Q-Sepharose (Pharmacia, USA) column in a FPLC equipment (Pharmacia, USA). The sample was injected in the balanced column with buffer A and was eluted by linear gradient up to 50% of buffer B (buffer A+1 M NaCl).

The purification second step was performed by chromatography in a Superdex 200 (Amersham, UK) molecular exclusion column. See FIGS. 6 and 7. For this, the chimera peak was concentrated in a Centriprep (Millipore, USA) tube and injected in the column for elution with PBS. The presence of the chimeric protein in the peaks was evaluated by SDS-PAGE.

The construction of the BLS-OMP31 chimeric gene was performed by using molecular biology techniques known in the art. See Sambrook, et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, New York, N.Y., 1989; Brown, Gene Cloning, Chapman & Hall, London, England, 1995; Watson, et al., Recombinant DNA, 2nd Ed., Scientific American Books, New York, N.Y., 1992 and Davis et al., Basic Methods in Molecular Biology, Elsevier Science Publishing Co., New York, N.Y., 1986, Alberts, et al., Molecular Biology of the Cell, 4^(th) Ed., Garland Science, New York, N.Y., 2002.

EXAMPLE 2 BLS-OMP31 Chimera Stability

The first proof that the BLS-OMP31 chimeric protein has adopted a decameric folding was obtained trough the light scattering technique. This procedure was used to calculate the molecular size of the proteins in solution. To conduct these assays, a molecular exclusion column was joined to a light scattering detector. As the protein eluted from the column its molecular weight was determined.

According to this method, the calculated BLS molecular weight was 163 kDa while that of the BLS-OMP31 chimera was 215 kDa. The theoretical molecular weights of the native BLS and BLS-OMP31 decamers were of 174.4 and 197.8 Kda, respectively. Taking to account that this method is 90% accurate, this result suggests that the BLS-OMP31 chimera forms a decamer very much alike the native BLS protein.

The folding chimeric proteins was studied through circular dichroism. The circular dichroism measurements were performed in the J-810 spectropolarimeter (Jasco, UK), set up at a reading speed of 100 nm/min, response time of 4 s and a band width of 1 nm. Quartz trays of 1, 2 or 5 mm (Hellma) were used. The samples were assayed in a 50 mM pH 7 phosphate buffer. The overlay of the circular dichroism spectra of the BLS-OMP31 chimera and native BLS showed that the general folding of both proteins were very similar. See FIG. 8. Thus, it was confirmed that the chimeric proteins folded properly like decamers, with a secondary structure comparable to that of the native protein.

Next, it was studied whether the substitutions at N-terminal of the chimeric proteins affected their stability. To this end, the induced denaturalization of the chimeras by guanidine hydrochloride (Gdm-HCl) and temperature was studied through circular dichroism.

From denaturalization-to-balance curves, it was possible to obtain several thermodynamic parameters, such as the change of free energy associated with unfolding. With this parameter, the conformational stability typical of a protein was evaluated. See Pace, et al, Methods Enzymol., 131: 266-80 (1986). To assess the change of free energy associated with the unfolding of each protein, the research data was adjusted to a theoretical descriptive curve. This diagram depicted the correlation of the equilibrium constant between the folded and unfolded stages of the chimeric protein and varying concentrations of the denaturalizing agent.

To conduct these experiments, the same amount of protein (0.1 μM of decamer) was incubated with increasing concentrations of the denaturalizing agent. The solutions for each point of the curve were prepared from a matrix solution of 6 M guanidine-HCl (ICN, ultra pure), 50 mM phosphate, pH 7. The samples were incubated for three hours at room temperature and were centrifuged before measurement. The circular dichroism measurements were performed in trays of 5 mm at 25° C. The reversibility of the denaturalization by guanidine of the BLS native protein and the BLS-OMP31 chimeric protein was thus demonstrated.

The denaturalization-to-balance curves were adjusted to a two step dissociation model. According to this model the decamer separated firstly into two equal pentamers. In the second step of denaturalization, each of these pentamers dissociated further into five unfolded monomers. The formulas describing this transition were derived from those already proposed for monomeric proteins. See Zylberman, et al, J. Biol. Chem., 279(9):8093-8101 (2004).

The thermodynamic values obtained for the native BLS and BLS-OMP31, show that the replacement of the BLS N-terminal end did not affect the decamer stability. See FIG. 9. Therefore, it was confirmed that the BLS chimeras form properly folded decamers and that their stability is similar to those of the native BLS.

EXAMPLE 3 BLS-OMP31 Chimera Antigenicity and Immunogenicity

The antigenicity of the BLS-OMP31 was studied by measuring its capacity to bind to a specific monoclonal antibody against the inserted peptide (A59/10F09/G10 monoclonal antibody) and to a specific monoclonal antibody against the native BLS protein (BI24 monoclonal antibody). See Vizcaíno, et al., Infect. Immun., 69(11):7020-28, (2001); Goldbaum, et al., J. Clin. Microbiol., 31:2141-2145 (1993). This procedure allows assaying the antigenicity of both the insert and the protein core. The antigenicity was assayed by ELISA. See FIG. 10.

The BLS-OMP31 was identified both by the monoclonal antibody against the native BLS and by the monoclonal antibody against the inserted peptide. The native BLS was only identified by the first antibody, as expected. This result indicates that the inserted peptide preserved its antigenic properties when displayed by the chimera. In addition, it was also showed that the folding of the chimera did not affect the affinity of anti-BLS antibody to the protein core. Both antibodies detected up to 20 ng of chimera per well.

Then, the BLS-OMP31 capacity to induce a specific humoral immune response against the inserted peptide was evaluated. This capacity was analyzed in mice with and without the assistance of adjuvants. The experiment was performed with two groups of five mice each. The “AF” group received three doses, by intraperitoneal route, of 25 ug of protein in emulsion with Freund adjuvant at 0, 20 and 40-day intervals. The first dose was administered with a complete Freund's adjuvant. The remaining doses were administered with an incomplete Freund's adjuvant. The “PBS” group had the same treatment but the chimeric protein was injected without adjuvant. Blood was drawn 7 days after the third immunization and the sera reactivity against the OMP31 membrane protein was assayed by ELISA. See FIG. 11.

A strong response against OMP31 was obtained in the mice immunized with the chimera and the adjuvant. The serologic response obtained from the mice immunized with the chimeric protein with and without the adjuvant was also relevant. These results show that mice immunized with the BLS-OMP31 chimera with or without adjuvant have specific immune responses against the inserted peptide.

A rabbit was injected with BLS-OMP31 chimera with adjuvant according to the following protocol:

First dose, day 0: 200 μg BLS-OMP31 in 1 ml of PBS+1 ml of complete Freund's adjuvant, by intramuscular injection.

Second dose, day 22: 200 μg BLS-OMP31 in 1 ml of PBS+1 ml of incomplete Freund's adjuvant (IFA), by subcutaneous injection.

Third dose, day 45: 200 μg BLS-OMP31 in 1 ml of PBS+1 ml of IFA, by intramuscular injection.

Fourth dose, day 155: 200 μg BLS-OMP31 in 1 ml of PBS+1 ml of IFA, by subcutaneous injection.

Blood samples were drawn at 31^(th), 52^(nd) and 180^(th) day. The samples were centrifuged and the serum was frozen.

The antisera collected after the 2^(nd), 3^(rd) and 4^(th) doses of the antigen were titrated by ELISA against the OMP31 membrane protein. See FIG. 12. The assayed antisera titer was of 3,200, 12,800 and 25,600 for sera corresponding to the 2^(nd), 3^(rd) and 4^(th) doses, respectively. The base line was defined as the maximum dilution capable of identifying the antigen over the negative serum. The immunized rabbit showed a strong specific immune response against the OMP31. Since the anti native BLS serum did not identify the OMP31, this high reactivity was due to a response of specific antibodies against the peptide inserted in the chimera. See FIG. 13, negative control.

The OMP31 protein used in the ELISA assays was produced recombinantly in E. coli. Since this molecule is a membrane protein, it cannot be kept in an aqueous solution; and was, therefore, obtained under denaturalizing conditions. In the assays performed, it was not demonstrated that the antisera were able to identify the OMP31 chimera in its native conformation as a bacterial membrane protein. This property is important to evaluate the potential effectivity of the chimera as an immunogen capable of providing humoral immunity against Brucella. To assess this property, ELISA assays were performed using a smooth and a rough strain of B. melitensis H38, as antigens. See FIG. 13. The reactivity of a serum against whole bacteria is difficult to evaluate in general due to the complexity of the antigen used. However, the assay showed that the anti BLS-OMP31 serum specifically identified the OMP31 insert in the membrane of the rough strain. The reactivity of this serum against the smooth strain was not different from that shown by the anti native BLS serum. This result is completely consistent with the data published for the A59/10F09/G10 monoclonal antibody. See Vizcaíno, et al., supra. This antibody, specific for the insert included in the BLS-OMP31 chimera, has strong reactivity with the rough, but not the smooth B. melitensis H38.

EXAMPLE 4 BLS-OMP31 Immunogenicity, as a Vaccine, to DNA

The codifying sequence for the BLS-Omp31 was subcloned in the vector pCI-neo (Promega, USA), including the restriction sites in the 5′ ends (framed) of the primers and the Kozak consensus sequence (underlined). Hence, the following oligonucleotides were built:

BLS-OMP31 “sense”: (SEQ ID NO: 35) 5′TAAGAA GAATCC  ACCACCATG  CAT ACC GCC GGT TA 3′. BLS-OMP31 “anti-sense”: (SEQ ID NO: 36) 5′TGT CCA CCA GTC AT GCTAGCT CAG ACA AGC GCG ATG C 3′.

Such sequence was amplified by PCR using the pET-BLS-OMP31 plasmid as a template. The PCR product and the vector were digested with the corresponding restriction enzymes and then a ligation reaction was performed. The obtained construct was checked by sequencing. The pCI-BLS-OMP31 plasmid was amplified in E. coli JM109 cells and further purified by “mega prep” columns (Quiagen, UK). DNA purity and concentration were assessed by spectrophotometry at 260/280 nm. The plasmid preparation contained less than 0.05 units of endotoxin per 100 μg of DNA, determined by a limulus amebocyte lysate analysis kit (Sigma, USA).

Groups of—Balb/c mice were inoculated with 100 μg of pCI-BLSOMP31 plasmid and the control plasmid without insert (pCI) in physiological solution by intramuscular (im) and intradermal (id) route at weeks 0, 2, 4 and 6. The animals blood was extracted by retroorbital route at days 0, 15, 30, 45, 60 and 75 after the first immunization. The sera were kept at −20 C for the detection of specific antibodies.

The anti-OMP31 humoral response induced by the immunization with the BLS-OMP31 DNA vaccine (pCI-BLSOMP31) was analyzed by indirect ELISA using the recombinant OMP31 protein as an antigen. After immunization, all animals developed a humoral immune response. A high level of the IgG isotype produced specifically against the Omp31 protein was observed. See FIG. 14.

The preparation, amplification, purification and use of pCI-BLS-OMP31 plasmid as a DNA vaccine was performed using molecular biology techniques and methods for the preparation and administration of pharmaceutical compounds known in the art. See Schleef, M, Ed, Plasmids for Therapy and Vaccination, Wiley-VCH Verlag GmbH, Weinheim, Germany, 2001.

EXAMPLE 5 Mixed BLS Chimeras

The fact that lumazine synthase of Brucella spp. dissociates reversibly when treated with high concentrations of guanidine chloride was used to construct mixed chimeras. See Zylberman, et al., J. Biol. Chem. 279 (9):8093-8101 Two chimeras with marked differences in their insert size and isoelectric points were constructed. This strategy was followed in order to distinguish more easily the decamers formed by the mixed chimeras.

To this end, the KETc1 peptide shown in FIG. 15 was used in addition to the OMP31 peptide already described. The KETc1 peptide derives from a protein of Tenia solium and has been described as highly protective against murine and pig neurocysticercosis. See Huerta, et al. Vaccine 20:62-266 (2001); Toledo, et al., Infect. Immun., 69:1766-1773 (2001).

The BLS-KETc1 chimeric protein was obtained according to the following protocol:

1. Cloning

-   -   a) The pBLS-OMP31 plasmid was digested with the Nsi I and Afl II         restriction enzymes to remove the codifying sequence         corresponding to the 27 amino acids from the 48-74 sequence of         the OMP31 protein. The OMP31 protein codifying sequence was         extracted.     -   b) The codifying sequence for the 14 amino acids of the KETc1         peptide was linked to the open cassette in a) by incubation         overnight of the open cassette of the pBLS-OMP31^(-OMP31)         plasmid with DNA T4 ligase enzyme at 16° C. The BLS-KETc1         reading frame was thus obtained. The insertion was confirmed by         the sequencing of the reading frame. This reading frame was         called BLS-KETc1 chimera, of SEQ ID NO:21, and the expression         plasmid, pBLS-KETc1.

This procedure can also be performed following the protocol indicated in step 1) of Example I through the cleavage of BLSm cassette (SEQ ID NO:12) with the Nsi and Afl I restriction enzymes and its further linkage with the KETc1 insert. Thus, the BLS-KETc1 reading frame and the pBLS-KETc1 plasmid are also obtained.

This experience was repeated using the DNA sequences of the mutated BLS SEQ ID NO:13, SEQ ID NO:14, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:17 and SEQ ID NO:18. Similar results were obtained.

2. Transformation

A competent strain of E. coli BL21 (DE3) bacteria was transformed by thermal shock with the pBLS-KETc1 plasmid obtained according to the protocol above. Afterwards, bacteria were cultured in agar plates including LB-agar/ampicilin to choose those transformed with the plasmid.

3. Expression and Purification of the BLS-KETc1 Chimeric Protein

2 ml of a LB/ampicilin medium was inoculated to a colony extracted from agar plates for small-scale expression tests. The colony was shaked and incubated at 37° C. The saturated culture was induced with 2 μl of 1M IPTG. Three hours later, 100 μl of culture was removed and centrifuged. The resulting pellet was resuspended in 25 μl of sample buffer 1× for its analysis by SDS-PAGE 17%

A 5-ml preculture of the transformed strains was cultured to saturation according to the step above with 500 ml of LB/ampicilin. The culture was incubated and shaked at 37° C. It was induced with 0.5 ml of 1M IPTG to reach an optical density of 0.6-0.8 at 600 nm The culture was removed three hours later and was centrifuged at 4,000 g for 20 minutes. The pellet was resuspended in 15 ml of suspension solution (50 mM Tris, 5 mM EDTA, 1% Triton X-100, pH 8.0).

The suspension was sonicated for at 1 minute intervals every minute for 5 minutes and was centrifuged at 20,000 g for 30 minutes. The pellet was resuspended in 15 ml of suspension solution without Triton X-100 and the sonicate process was repeated. The procedure was repeated for a third time. The chimera expressed in the cytoplasm was contained in three sonicate supernatants while inclusion bodies were contained in the pellet.

The inclusion bodies were resuspended in PBS buffer with 8 M urea and were left overnight at room temperature. The resuspension was dialyzed against PBS for two days with a buffer change. The sample was centrifuged and the supernatant was dialyzed against buffer A (50 mM Tris/HCl, pH 8.5). The first purification step was performed by anionic interchange chromatography in a MonoQ or a Q-Sepharose (Pharmacia, USA) column in a FPLC equipment (Pharmacia, USA). The sample was injected in the balanced column with buffer A and was eluted by linear gradient up to 50% of buffer B (buffer A+1 M NaCl).

The purification second step was performed by chromatography in a Superdex 200 (Amersham, UK) molecular exclusion column. For this, the chimera peak was concentrated in a Centriprep (Millipore, USA) tube and injected in the column for elution with PBS. The presence of the chimeric protein in the peaks was evaluated by SDS-PAGE.

The construction of the BLS-KETc1 chimeric gene was performed by using molecular biology techniques known in the art. See Sambrook, et al., supra; Brown, supra; Watson, et al., supra; Davis et al., supra, Alberts, et al., supra.

The BLS-OMP31 and BLS-KETc1 chimeras were unfolded in 2 M of guanidine chloride, mixed in equimolar concentrations and re-associated through dialysis. Adding 2 M guanidine, the decamers were separated thus generated pentamers that preserved their secondary structure. When the guanidine was removed through dialysis, the pentamers were re-associated forming decamers again. See Zylberman, et al., J. Biol. Chem., 279(9): 8093-8101 (2004). In this manner, a mixture of BLS chimeras was produced. See FIG. 16.

The re-association product was purified by interchange chromatography in a MonoQ (Amersham, UK) anionic interchange column. The results were compared to the elution profile of each separate chimera (a sample without dissociation) according to the following protocol: the BLS-KETc1 chimera was eluted at 16.8% of buffer B (this particle was estimated the most basic in view of insert theoretical isoelectric point) and the BLS-OMP31 chimera was eluted at 35.8% of the same buffer. The re-associated sample was separated yielding three different peaks, the first corresponded to the pure BLS-KETc1 chimera; the second and largest peak corresponded to the mixed chimera and the last peak corresponded to the pure BLS-OMP31 chimera. See FIG. 17 A.

The sample corresponding to the second peak was analyzed by SDS-PAGE and native PAGE. The results demonstrated that the sample corresponded to a mixed chimera formed by KETc1 peptide displayed in the five amino termini of one pentamer and by OMP31 peptide displayed in the five amino termini of the other pentamer. See FIGS. 17 B1 and B2.

This outcome showed that proposed strategy of separating, mixing and re-associating the modified proteins was effective to yield a mixed chimera where five copies of two different peptides were displayed by the BLS decameric structure. See FIG. 16. The mixtures may have different characteristics depending on the nature of the inserts (e.g. one insert might be directed to an specific cell traffic while the other might induce a particular immune response).

EXAMPLE 6 Immunization with Mixed BLS Chimeras

The mixed BLS-OMP31-KETc1 chimeras was administered with adjuvants to mice to evaluate its capacity to induce a specific humoral immune response. The experiment was performed with a group of five mice. The group received three doses of 25 μg of protein in emulsion with a Freund's adjuvant by intraperitoneal route at 0, 20 and 40 days. The first dose was applied with a complete adjuvant. The second and third doses were applied with an incomplete adjuvant. Blood was drawn 7 days after the third immunization and the sera reactivity was assayed against the OMP31 and KETc1 synthetic peptides by ELISA. See FIG. 18.

A strong response against both peptides was obtained in immunized mice with the mixed chimeras with adjuvant. This demonstrated that mice immunized with the BLS-OMP31-KETc1 mixed developed simultaneously a specific immune response against both inserts.

EXAMPLE 7 Cellular Immune Response Against BLS Chimeras

Groups of five BALB/c mice were immunized with 50 μg/mouse of the BLS-KETc1 chimera emulsified in saponin and with 10 μg/mouse of the KETc1 synthetic peptide emulsified in saponin to assess the specific cellular immune response induced by the BLS-KETc1 chimera against the inserted peptide. The mice were immunized twice within a 10-day interval by subcutaneous route.

The spleens of both groups were aseptically removed three days after the last immunization. The spleen cells were resuspended in an RPMI 1640 Gibco (InVitrogen Corp., USA) culture medium, supplemented with L-glutamine (0.2 mM), 2-mercaptoethanol (0.05 mM), non-essential amino acids (0.01 mM), penicillin (100 U/ml), streptomycin (100 μg/ml) and fetal bovine serum 10% (FBS). A culture medium, the KETc1 peptide or the BLS-KETc1 chimera (10 μg/ml) were added to different cell cultures. The cells were suspended in flat-bottom culture microplates at a concentration of 2×10⁵ cells per 200 μl of final volume. They were kept in a 5% C0₂ humidified environment at 37° C.

After 72 hours, 1 μCi of [methyl-³H] timidine (Amersham Biosciences, UK) was added to each culture. The cells were seeded and the tritrated timidine level of incorporation was measured in a 1205 Betaplate™ liquid scintillation counter (Wallac Oy, FI). All the assays were performed in triplicate.

The assay showed that the spleen cells of mice immunized with the BLS-KETc1 chimera proliferated in cultures in the presence both of the peptide and the chimera. This result clearly indicated that the BLS-KETc1 chimera was able to induce a specific cellular immune response against the KETc1 peptide inserted in BLS. See FIG. 19.

EXAMPLE 8 Multidisplay of Protein Domains by BLS Chimeras

The BLS can be modified to display not only peptides but also complete protein domains in its ten amino termini. In order to demonstrate this alternate use a BLS-RBD3 chimera was constructed by linking the modified BLS codifying sequence and the codifying sequence of the RBD3 proteic domain of the murine protein Staufen-1. See FIGS. 20 and 21.

The BLS-KETc1 chimeric protein was obtained according to the following protocol:

1. Cloning

-   -   a) The pBLS-OMP31 plasmid was digested with the Nsi I and Afl II         restriction enzymes to remove the codifying sequence         corresponding to the 27 amino acids from the 48-74 sequence of         the OMP31 protein. The OMP31 protein codifying sequence was         extracted.     -   b) The codifying sequence for the 75 amino acids of the RBD3         domain of the murine protein Staufen was linked to the open         cassette in a) by incubation overnight of the open cassette of         the pBLS-OMP31-OMP31 plasmid with DNA T4 ligase enzyme at 16° C.         The BLS-RBD3 reading frame was thus obtained. The insertion was         confirmed by the sequencing of the reading frame. This reading         frame was called BLS-RBD3 chimera, of SEQ ID NO:22, and the         expression plasmid, pBLS-RBD3.

This procedure can also be performed following the protocol indicated in step 1) of Example 1 through the cleavage of BLSm cassette (SEQ ID NO: 16) with the Nsi and Afl I restriction enzymes and its further linkage with the RBD3 insert. Thus, the BLS-RBD3 reading frame and the pBLS-RBD3 plasmid are also obtained.

This experience was repeated using the DNA sequences of the mutated BLS SEQ ID NO:13, SEQ ID NO:14, SEQ ID NO:15, SEQ ID NO:16, SEQ ID NO:17 and SEQ ID NO:18. Similar results were obtained.

2. Transformation

The pBLS-RBD3 plasmid obtained according to the above protocol was inserted in E. coli BL21 (DE3) bacteria by thermal shock transformation. Afterwards, the bacteria were seeded in an LB medium in the presence of ampicillin. The gene expression was induced with IPTG 1 mM for 4 hours at 28° C.

3. Expression and Purification of the BLS-RD3 Chimeric Protein

The protein was expressed in inclusion bodies, washed with 4 and 6 M urea solutions and solubilized in a buffer Tris/HCl 50 mM, urea 8 M, EDTA 5 mM, β-ME 5 mM, PMSF 1 mM, pH 8 by magnetic stirring for 16 hours at 4° C. The solubilized protein was purified under denaturalizing conditions in a Q-Sepharose ionic interchange column applying a linear gradient between 0 and 1 M NaCl in a buffer Tris/HCl 50 mM, 8 M urea, pH 8.5. The eluted protein was refolded by dialysis against the PBS buffer and purified by a heparin Hyper D column. For elution, a buffer Tris/HCl 50 mM, NaCl 1.2 M, pH 8 was used.

FIG. 22 shows the SDS-PAGE, circular dichroism and light scattering analyses of the BLS-RBD3 chimera obtained through the method described above.

The SDS-PAGE analysis shows the high degree of purity of the BLS-RBD3 chimera obtained. The small anomaly observed in electrophoretic mobility is attributed to the high density of the RBD3 domain positive charge. The similarity of the BLS-RBD3 circular dichroism spectrum with its theoretical spectrum, calculated by the combination of the spectra of the BLS and the RBD3 domain of the isolated murine protein Staufen-1, indicated that the chimera was well-folded. The chimera molecular weight (257 kDa), calculated from its run in the molecular filtering column connected in series to a light scattering detector and a refraction index detector, indicated that BLS-RBD3 chimera presented a decameric structure.

The construction of the BLS-RBD3 chimeric gene was performed by using molecular biology techniques known in the art. See Sambrook, et al., supra; Brown, supra; Watson, et al., supra; Davis et al., supra, Alberts, et al., supra.

EXAMPLE 9 Production of Wide Spectrum Antibodies by Immunization with BLS Chimeras

The BLS-Staufen chimera was used as an immunogen to obtain antibodies against the Staufen RBD3 domain. 5 Balb/c mice were inoculated with 80 μg of the BLS-RBD3 chimera in a buffer 200 μl HCl 50 mM, NaCl 1.2M, 50 mM phosphate, pH 8 without adjuvant twice, at a 14-day interval by intraperitoneal route. As a control, 5 mice of the same strain were immunized with a mixture of BLS proteins and the Staufen RBD3 domain, in the same chimera-including mass. The mice were bleeded through retroorbital punction fifteen days after the last immunization. A serum was prepared through centrifugation at 1000×g for 10 min. Sera reactivity against RBD3 was assayed by ELISA in 96-well plate with the glutathione S-transferase-RBD3 (GST-RBD3) fusion protein. Mouse anti-immunoglobulin conjugated to caprine peroxidasa (DakoCytomation, USA) was used as a secondary antibody. The reaction was developed with orthophenildyamin (OPD) and was stopped with 4 N sulphuric acid. The optical density was determined by an ELISA reader at 492 nm

FIG. 23 shows a representative example of the humoral immune response developed by both groups. As observed, immunization with the BLS-RBD3 chimera caused a strong anti-RBD3 antibody response. No reactivity was observed against the peptide in mice inoculated with the BLS and RBD3 mixture.

EXAMPLE 10 Production of Monoclonal Antibodies by Immunization with BLS Chimeras

The capacity to generate specific monoclonal antibodies against the OMP31 peptide was assessed from splenocytes of mice immunized with the BLS-OMP31 chimera. The experiment was performed with a group of five mice. The group received three doses, by intraperitoneal route, of 25 μg of protein in emulsion to the medium with Freund's adjuvant at 0, 20 and 40-day intervals. At day 60, 25 μg of BLS-OMP31 dissolved in PBS was inoculated by peritoneal route in the mouse that showed a better response against the OMP31 peptide. The spleen of such mouse was removed and the splenocytes were merged with the NSO myeloma cells. The resulting hybridomas were selected in a HAT medium and their culture supernatants were assayed to measure reactivity against the OMP31 peptide by ELISA. The hybridoma that showed a higher reactivity was cloned by limit dilution. FIG. 24 shows the AcMo 37F7 reactivity against the OMP31 peptide and the whole OMP31 protein. A strong response against both was obtained. This demonstrated that mice immunized with the BLS-OMP31 chimera developed a specific immune response against the inserted peptide. This experience also shows that specific monoclonal antibodies could be produced using the BLS chimeras.

EXAMPLE 11 Use of BLS Chimeras as Biosensors

Biosensors allow the detection of a specific interaction among macromolecules, which is visualized by the increase of a signal proportional to the mass accumulation on a reactive surface. The BLS-OMP31 modified protein was used to study the application of the BLS chimeras as a peptide and proteic domain carrier for the development of biosensors. To this end, the reaction between the BLS-OMP31 and the AcMo 37F7 described in the previous example was analyzed further.

The BLS-OMP31 chimera was used to derivatize a dextran carboximethyl plate (IAsys Affinity Sensors, Thermo, USA). For that purpose, a solution including 80 μg/ml of BLS-OMP31, in a buffer of 10 mM sodium acetate pH 5.5, was incubated in a plate previously derivatized by the EDC/NHS reagent. After immobilizing a signal corresponding to 800 arc sec (equal to 5 ng of antigen), the reactive surface was blocked with diethylamine. After derivatization, the anti-OMP31 AcMo 37F7 reactivity was studied, for which 50 μl of culture supernatant were incubated in the previously activated plate.

As observed in FIG. 25, the AcMo 37F7 reacted strongly, providing a signal of approximately 300 arc sec. In the separation phase, the buffer PBS+Tween was washed and added, observing a drop in the signal corresponding to the AcMo separation of the solid phase. This example clearly shows that the chimera is able to detect antibodies directed against the peptide in the biosensor.

EXAMPLE 12 Activation of Dendritic Cells by BLS

The BLS capacity of activating dendritic cells was analyzed. To that end, the activation levels of different markers were studied in these cells 18 hours after incubation with BLS. Bone marrow cells from Balb/c mice were cultured in Petri plates with a RPMI medium with 2 mM L-glutamine, 100 U/ml-penicillin, 100 μg/ml streptomycin, 50 μM 2-mercaptoethanol and 10% fetal bovine serum (medium R10), supplemented with mouse granulocyte and macrophages colony stimulating factor (mGM-CSF) in an incubator with a 5% CO₂ environment at 37° C. The culture medium was replaced at days 3, 6 and 8. At day 9, the non-adhered cells were taken and centrifuged at 300×g for 8 minutes. The cells were then incubated at a concentration of 2×10⁶ cells/ml in a final volume of 1 ml with BLS (1, 5 or 10 μM) or without BLS in R10 medium for 18 hours (n=4). Afterwards, 4×10⁵ cells per 200 μl of final volume were centrifuged and incubated with the following monoclonal antibodies (Pharmingen) conjugated to fluorescein isothiocyanate (FITC): anti-CD40, anti-CD80, anti I-A^(d) or anti-CD86, and with the anti-CD11c monoclonal antibody conjugated to phycoerythrin (PE). Three washings were performed and the cells were extracted with a FACScan cytometer (Becton Dickinson, USA). The obtained data was analyzed with the CellQuest (Becton Dickinson, USA) software.

In the cells incubated with BLS, within the subpopulation of CD11c⁺ (75-80%), significant increases were observed in the percentages and mean fluorescence of cells expressing CD40, CD80, I-A^(d) y CD86. The experiment was performed three times, obtaining similar results. FIG. 26 shows representative histograms of the CD40 expression (A) and of the I-A^(d) (B) in CD11c⁺ cells treated with or without BLS.

A similar activation by BLS was observed in dendritic cells of C3H/HeJ mice (non responders to LPS) or when pre-incubating the BLS protein with polymyxin B, so as to eliminate LPS of E. coli.

These results demonstrated that the BLS is able to activate dendritic cells.

EXAMPLE 13 Production of Molecular Assemblies with Protein Domains through Adaptor Peptides Linked to BLS Chimeras

The BLS protein could be modified in its amino termini to display whole proteic domains. This could be accomplished by the formation of molecular assemblies. In these clusters, complementary heterodimeric peptides are incorporated into the modified BLS protein and the target. Afterwards, the high affinity between the heterodimers links the target molecule and the modified BLS protein. The use of high affinity heterodimers is useful to avoid affecting the proper folding of the carrier protein. To demonstrate this application of the BLS chimeras, two heterodimerization peptides known in the art, RR₁₂EE₃₄₅L y EE₁₂RR₃₄₅L, were used. See Moll, et al., M Protein Sci., 10:649-655 (2001). See FIG. 27. This strategy allowed the construction of molecular assemblies, including ten copies of the domain combined with the BLS. The assembly was performed in vitro, which made possible to control the stoichiometry of the process. This system also enables expressing the antigen in a recombinant system different from BLS. See FIG. 28A and FIG. 28B.

1. Construction of Fusion Protein BLS-RR₁₂EE₃₄₅L

The peptide RR₁₂EE₃₄₅L was cloned in the N-terminal end of the BLS. See FIGS. 28A, 28B and 29. The K₄₉ residue located in BLS and RR₁₂EE₃₄₅L linker region was substituted for serine. The BLS-RR₁₂EE₃₄₅L chimeric gene was cloned in the pET11a vector. A competent strain of E. coli BL21 (DE3) bacteria was transformed with the resulting vector. Afterwards, the bacteria were cultured in a LB-agar/ampicillin culture medium The gene expression was induced with 1M IPTG for 16 hours at 37° C. The protein was expressed in the inclusion bodies.

The inclusion bodies were washed with a buffer 50 mM Tris/HCl, 5 mM EDTA, 5 mM β-ME, 1 mM PMSF, pH 8. The dissolved protein was treated with a buffer 50 mM Tris/HCl, 8 M urea, 5 mM EDTA, 5 mM β-ME, 1 mM PMSF, pH 8 and stirred magnetically for 16 hours at 4° C. The resulting BLS-RR₁₂EE₃₄₅L chimera was purified under denaturalizing conditions by anionic interchange chromatography in a Q-Sepharose (Pharmacia, USA) column. The sample was eluted using a buffer 50 mM Tris/HCl, 8 M urea, pH 8.5 under a linear gradient of 0 to 1 M NaCl. The fusion protein was assayed by SDS-PAGE and light scattering analyses. See FIGS. 30 and 31.

The SDS-PAGE analysis showed that the fusion protein BLS-RR₁₂EE₃₄₅L had a high level of purity. The molecular weight of the protein, as determined by the light scattering technique, was 224 kDa. In addition, the protein showed a high-quality CD signal in the remote UV spectrum These results suggest that the fusion protein is well folded and observes a decameric structure similar to the native BLS protein when in the presence of 8M urea. The BLS structure is distorted at room temperature when the urea concentration is decreased. This is probably due to the binding of the RR₁₂EE₃₄₅L with itself.

2. Construction of Peptide EE₁₂RR₃₄₅L

The peptide EE₁₂RR₃₄₅L was cloned in the C-terminal end of protein glutathione S-transferase (GST). This peptide is complementary to the RR₁₂EE₃₄₅L peptide displayed by the BLS fusion protein. See FIG. 32.

The EE₁₂RR₃₄₅L peptide gene was cloned in the pGEX-4T1 vector. A competent strain of E. coli BL21 (DE3) bacteria was transformed with the resulting vector. Afterwards, the bacteria were cultured in a LB-agar/ampicillin culture medium at 37° C. The gene expression was induced with 1 mM IPTG for 16 hours at 37° C. The bacteria were then sonicated.

The resulting EE₁₂RR₃₄₅L peptide was purified as a GST fusion protein using a glutathione/agarose matrix. The coupled complex was set in a column and was washed with a buffer 50 mM Tris, pH 8 until the peptide was absent from the eluent. Afterwards, the matrix was incubated with thrombine for 16 hours at room temperature to cleave the EE₁₂RR₃₄₅L from GST fusion protein. The peptide was then eluted with a buffer 50 mM Tris, pH 8 to purify it further. The resulting EE₁₂RR₃₄₅L peptide had a high level of purity.

3. Formation of Molecular Assembly Between Fusion Protein BLS-RR₁₂EE₃45L and Peptide EE₁₂RR₃₄₅L

One part of the fusion protein BLS-RR₁₂EE₃₄₅L was preincubated with 8 M urea, 50 mM Tris, 0.5 M NaCl, pH 8 for 15 minutes at 30° C. Four parts of the peptide EE₁₂RR₃₄₅L were preincubated in a buffer 50 mM Tris, 0.1 M NaCl, pH 8 for 15 minutes at 30° C. The fusion protein and peptide were mixed and incubated for 15 minutes at 30° C. The mixture remained soluble after incubation.

The resulting molecular assembly was assayed by light scattering analysis and its theoretical molecular weight was calculated (MW: 222.1 kDa). See FIG. 34. This analysis showed that approximately 10 EE₁₂RR₃₄₅L peptides (MW: 5.6 kDa) coupled to the BLS-RR₁₂EE₃₄₅L decamer (MW: 222.1 kDa). See FIG. 35.

In addition, the assembly showed a high-quality CD signal in the remote UV spectrum. These results suggest that molecular assemblies formed with modified BLS proteins using this technique are viable.

The present invention has been described in some detail and exemplified to facilitate its understanding and reproducibility. Certain changes in the form and detail can be made by anyone skilled in the art without departing from the true object and scope of the claims of the present invention. All the publications quoted herein are incorporated in their totality as references to the description of the invention.

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What is claimed is:
 1. Isolated chimeric proteins comprising a peptide, a polypeptide or a proteic domain linked to a modified lumazine synthase protein from Brucella spp, wherein either the first 8 N-terminal residues of the modified protein have been deleted or the nucleotide sequences encoding the first 8 N-termini residues of the modified protein are replaced with DNA sequences comprising restriction sites for enzymes Nsi I and Afl II, wherein the amino acid sequence of the modified protein consists of SEQ ID NO:7.
 2. The isolated chimeric proteins, according to claim 1, wherein the linked peptide, polypeptide or proteic domain is homologous or heterologous.
 3. The isolated chimeric proteins, according to claim 1, wherein the linked peptide, polypeptide or proteic domain is an antigen, toxin, agent or segment thereof, capable of inducing an immune response in an eukaryotic organism.
 4. The isolated chimeric proteins, according to claim 3, wherein the linked peptide, polypeptide or proteic domain is an antigen, toxin, agent or segment thereof of bacterial, viral or parasitic origin.
 5. The isolated chimeric proteins, according to claim 3, wherein the antigen is the Outer-membrane protein from Brucella melitensis fused to Brucella spp. lumazine synthase (BLS-OMP31) or functional segments thereof.
 6. The isolated chimeric proteins, according to claim 3, wherein the antigen is the Taenia crassiceps recombinant antigen fused to Brucella spp. lumazine synthase (BLS-KETc 1) or functional segments thereof.
 7. The isolated chimeric proteins, according to claim 3, wherein the antigen is murine Staufen-1 double-stranded RNA-binding domain 3 fused to Brucella spp. lumazine synthase (BLS-RBD3) or functional segments thereof.
 8. The isolated chimeric proteins, according to claim 3, wherein the immune response is humoral or cellular.
 9. The isolated chimeric proteins, according to claim 3, wherein the eukaryotic organism is a bird, fish or mammal.
 10. The isolated chimeric proteins, according to claim 9, wherein the eukaryotic organism is a mammal.
 11. The isolated chimeric proteins, according to claim 10, wherein the mammal is a human, a rabbit or a mouse.
 12. The isolated chimeric proteins, according to claim 3, wherein the linked peptide, polypeptide or proteic domain is an antigen, toxin, agent or segment thereof which induces an immune response in vitro or in vivo.
 13. The combination of two or more isolated chimeric proteins, according to claim 1, wherein the peptides, polypeptides or proteic domains linked to each modified protein are different.
 14. The combination of two or more isolated chimeric proteins, according to claim 1, wherein the peptides, polypeptides or proteic domains linked to each modified protein are identical.
 15. The combination of one or more isolated chimeric proteins, according to claim
 1. 16. A pharmaceutical composition comprising at least one of the isolated chimeric proteins according to claim
 1. 17. A pharmaceutical composition, according to claim 16, comprising an acceptable pharmaceutical excipient.
 18. A pharmaceutical composition, according to claim 17, wherein the acceptable pharmaceutical excipient is an adjuvant.
 19. A pharmaceutical composition, according to claim 18, wherein the adjuvant comprises a Freund's adjuvant, a MDP dipeptide, saponin, tyrosine stearate, aluminum hydroxide, lymph cytokines, the native protein of lumazine synthase of Brucella spp or the modified proteins of lumazine synthase of Brucella spp.
 20. A pharmaceutical composition comprising at least one of the isolated chimeric proteins according to claim
 1. 21. A pharmaceutical composition, according to claim 20, comprising an acceptable pharmaceutical excipient.
 22. A pharmaceutical composition, according to claim 21, wherein the acceptable pharmaceutical excipient is an adjuvant.
 23. A pharmaceutical composition, according to claim 22, wherein the adjuvant comprises a Freund's adjuvant, a MDP dipeptide, saponin, tyrosine stearate, aluminum hydroxide, lymph cytokines, the native protein of lumazine synthase of Brucella spp or the modified proteins of lumazine synthase of Brucella spp.
 24. A biosensor comprising a base attached to at least one isolated chimeric protein of claim 1, wherein said base is connected to a means for measuring the interaction of a ligand with said isolated chimeric protein.
 25. A biosensor, according to claim 24, wherein the ligand is an antibody.
 26. Protein conjugates comprising a ligand linked to the peptide, polypeptide or proteic domain connected to the modified proteins of lumazine synthase of Brucella spp. according to claim
 1. 27. The protein conjugates according to claim 26, wherein the ligand is linked to the peptide by a covalent bond.
 28. The protein conjugates, according to claim 26, wherein the link is non-covalent.
 29. The protein conjugates according to claim 26, wherein the ligand and the chimeric protein are linked through connecting sequences of a heterodimerization domain.
 30. The isolated chimeric proteins according to claim 1, wherein their quaternary structure is a decamer.
 31. The protein conjugates according to claim 26, wherein the ligand is linked to the peptide by a peptide bond.
 32. The protein conjugates according to claim 26, wherein the ligand and the chimeric protein are linked through connecting sequences encoding a leucine zipper.
 33. A method to induce an immune response in an eukaryotic organism comprising the administration of an effective amount of a pharmaceutical composition according to claim 16 to the organism.
 34. A method, according to claim 33, wherein the immune response is humoral or cellular.
 35. A method, according to claim 33, wherein the pharmaceutical composition is administered simultaneously or sequentially.
 36. A method, according to claim 33, wherein the eukaryotic organism is a bird, fish or mammal.
 37. A method, according to claim 33, wherein the eukaryotic organism is a mammal.
 38. A method, according to claim 37, wherein the mammal is a human, a rabbit or a mouse.
 39. A method, according to claim 33, wherein the pharmaceutical composition is administered by a subcutaneous, intravenous, intraperitoneal, intramuscular, oral or nasal routes or through a needle-free injection system. 